Alkaline cleaning composition



Patented July 14, 1942 UNITED STATES PATENT OFFIC j 2,289,578

v ALKALINE CLEANING oomrosrrion Harry H. Hull, Chicago Heights, andJoseph Janota, In,

Crete, Ill., asaiznors to The Diversey Corpo ation, a, corporation ofIllinois No Drawing.

Application December 5, 1940, Serial No. 368,736

.4 Claims. (cl. 252-135) In hard water, however, strong caustic sodasolution has the disadvantage that the calcium and magnesium of the hardwater will precipitate on the bottles and the automatic machineryordinarily employed, to form an adherent carbonate film.

In washing bottles or other shaped articles, on a large scale, theoperation is usually carried out on a continuous metal conveyor passingthrough a strong, hot, caustic alkali solution.

The conveyor is equipped with means for holding the objects to bewashed, these being usually pockets or hooks. When pockets are employed,the objects are carried through in them, the pockets being full of hotcaustic solution during the passage through ,the solution. Thereafterthe objects are discharged from the pockets and rinsed in rinsing water.The wet conveyor pockets are refilled with fresh objects and the cyclerepeated. Usually the rinse water is fresh water containing somemagnesium and calcium hardness and this hardness is precipitated uponthe conveyor pockets and chains, or upon the hooks, if hooks are-used.This precipitation occurs when the conveyor covered by a film of hardwater enters the strong caustic solution. The caustic causes theprecipitation of the calcium and magnesium in the form of a hardadherent film and this operation is repeated every time the conveyorre-enters the solution. As a result, a continuous and ultimately seriousbuildingup of scale on the conveyor pockets, hooks, and other objectsoccurs, and this also tends to occur on the bottles or other objectswhich are entering the solution, either because they are partiallywetted with hard water by contact with the wet conveyor parts, orotherwise wet, or due to the proximity of the wetted conveyor partsduring the precipitation operation.

If orthophosphate is added to the caustic alkali solution, theprecipitate of calcium and magnesium is in the form of an insolublephosphate, but this film likewise is adherent to the conveyor and thearticles being conveyed. Furthermore, the presence of orthophosphatewill permit an additional precipitation in the rinse bath.

The addition of alkali metal pyrophosphate to the caustic soda bathresults in the formation of an adheret calcium pyrophosphate scale whenhard water is contacted.

It has now been discovered, however, that if a cleaning composition ismade up of a pre-' dominant proportion of caustic alkali, and alkalimetal pyrophosphates and orthophosphates are added thereto in acarefully controlled relationship, the hard water impurities may bepreclpiated as phosphates at such a slow rate that the film is totallyeliminated or may be reduced to such an extent that it is notappreciable.

The preferred composition consists essentially of the following: y

a Per cent Caustic soda (commercial) 82.5

Tetrasodlum pyrophosphate (anhydrous) 10.0

Trisodium phosphate (crystalline) 7.5

The amount of tetrasodium pyrophosphate should be at least as much asthe trisodium phosphate, and should not bemore than over four times asmuch as the trisodium phosphate.

This means a ratio of pyrophosphate P205 to orthophosphate P205 3-to-1and 12-to-1.

between approximately The caustic alkali is preferably at least of thetotal of the alkali and phosphate ingredients, and is not greater thanapproximately 94%.

As an example of a substantially minimum caustic alkali concentration, acomposition may be employed containing:

Per cent Caustic soda '10 Tetrasodium pyrophosphate 20 Trisodiumphosphate 10 On the other hand, a composition employing:

was satisfactory at the other end of the range. This means a range oforthophosphate 2 I f aesama P205 of from approximately 0.35% toapproximately 1.9%, and a pyrophosphate P105 content from approximately2.1% to 10.6%.

Phosphoric or pyrophosphoric acids or acid salts may be employed,provided the caustic alkali is provided in sufllcient excess to make upior the loss of alkalinity thus introduced.

The concentration of the aqueous solution of the cleaning compositionwill depend of course upon the hardness of the water employed. Forexample, with water containing about 800 P.P.M. of hardness, a causticsoda ccncentration of about 3% is preferred.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom.

What we claim as new, and desire to secure by Letters Patent, is:

1. A composition of matter for use on automatic washing machineryemploying hot detergent solutions in connection with hard waterconsisting essentially of a predominant proportion of a caustic alkali,a relatively small proportion or an alkali metal pyrophosphate and analkali metal orthophosphate, the amount of the caustic alkali being atleast 70% of the specified ingredients, and the ratio of pyrophosphateP205 to one part of orthophosphate P205 being between approximately 3 to12 parts by weight, 30

whereby scale formation on the automatic washing machinery issubstantially prevented.

2. A composition of matter for use on automatic washing machineryemploying hot detergent solutions in connection with hard waterconsisting essentially 0!:

Per cent by weight Sodium hydroxide 70-94 Anhydrous sodium pyrophosphate20 4 l0 Crystalline sodium orthophosphate 10- 2 3. A composition ofmatter for use on automatic washing machinery employing hot detergentsolutions in connection with hard water consisting essentially of:

Per cent by weight Caustic soda; 80-85 Anhydrous tetrasodiumpyrophosphate 9-12 Crystalline trisodium orthophosphate 6-10 HARRY H.HULL. JOSEPH JANOTA, JR.

